This invention relates to solar energy heating systems and more particularly to a system using water as the heat collection and transfer medium.
One of the primary problems of solar energy systems which uses water is damage caused by freezing of the water in exposed portions of the system. One solution to this problem is to circulate warmed water through exposed portions of the system during periods when no solar radiation is available. This, however, uses energy which otherwise is wasted.
Another widely used arrangement for meeting the freeze damage problem is the drain-back system in which the water in the exposed portions of the system is replaced with air during periods when solar radiation is not available. This requires sufficient protected storage capacity in the system to accommodate the necessary volume of air during solar operation, or the drain-back water volume during shut-down. However, such a storage facility is serially connected in the system so that during operation the water heated by solar radiation is circulated therethrough, and, to some extent, held therein. Accordingly, extensive insulation of the storage facility is required to reduce loss of heat. This is both costly and inconvenient.